2 big reasons:
1 - they aren’t trying, they’re busy figuring out how the world works and not terribly concerned with whose religious beliefs are challenged by their findings
2 - you can’t prove a negative, which they know, which is why 1
You can prove a negative. First you determine all possible ways for it to be positive - then eliminate all of them.
This is why Atheists are full of it. They lack the tiniest minuscule faction of knowledge of everything yet claim with absolute certainty they know there is no God. There is noway they can KNOW that. It’s only their personal opinion based on belief with faith mankind will never find enough positive evidence to convince them God exists. Thus Atheism is a belief based on faith = a religion.
IMHO opinion Atheists do believe in God but are terrified of him - why else are they so emotional and hateful of something they do not believe in?